What is meant exactly by 'Deformable Mesh Area'? (context: Was Reading when/when not to use triangles)
Think of an ocean surface, various sizes of waves.
where all verticles move (try it in blender with ocean modifier).
You don't get strange artifacts with simulating that with quads
Not even if you later to decide to subdivide it.
Clean topology makes life easier, but there can be exceptions to the quads rule.
In some cases a tris might bend better, depending on the shape you might need a quad to have some bending angle divinding it into 2 tris.